The term shock, used already in the 19th century, was defined to characterize the alarming symptoms known to result from a wide variety of causes, both physical and psychic. One of the most frequently encountered types of shock is the traumatic one, caused after severe injury. As a result, a disturbance of fluid balance occurs which is manifested by a decreased volume of blood and tissue perfusion. Other changes, both chemical and pathologic may occur in a traumatic shock, including decreased coagulability of the blood.
There is a substantial agreement among all authorities in respect to the fact that incompatibility between blood volume and vascular volume due to loss of blood or other body fluids by whatever means or by pathologic dilatation of the vascular bed, is considered the most important initiating factor in shock. Accordingly there is a search for devices which provide an easy and immediate treatment for shock. In this connection it is perhaps interesting to cite a publication on this subject by Dr. R. L. Krome (Annals of Emergency Medecine, Aug. 14, 1985, 14/713): "It is fascinating that shock, considered at one time to have been researched out, is now fully resuscitated as a field of study". Early investigations examined a wide variety of possible therapeutic routes without fully understanding the pathophysiology of the problem. Today it is generally understood that although shock is associated with and is usually diagnosed mainly by a systolic blood pressure reading of less than 80 to 90 mm Hg, it is the reduced perfusion of few critical organs (namely the heart, brain, kidneys, liver and the intestines) which cause the severe pathophysiological consequences of shock. Among the events which cause shock the following are particularly mentioned: spontaneous rupture of blood vessels, i.e. abdominal aneurism, leg veins esophageal vasices etc., any accident which causes severe blood loss through an open injury, and sepsis or anaphylaxis which cause pathologic dilatation. Treatment of shock depends to some extent on the nature of the injury or disease responsible for its develoment. Attention is first directed to restoration of adequate balance between blood volume and vascular volume and to prevention of further loss of blood. In case of severe injury to the extremities, the part is immobilized. Prevention of loss of body heat is accomplished by use of covers; also elevation of the legs may be helpful to enable the draining of blood from the legs back into the critical organs such as the heart, brain kidneys and lung circulation so that they are resupplied with oxygenated blood. The usefulness of simple bandage applied the legs is limited in returning blood to the central vessels due to the range of pressure required.
After the second world war, an elegant device for shock treatment was suggested. It is the so called Medical Anti-Shock Trousers (MAST). The device is designed to counteract hypovolemic shock by the application of counterpressure around the legs and abdomen, producing an artificial peripheral resistance, and ensuring adequate to the critical organs perfusion. The device has the configuration of trousers, wherein air chambers surrounding the legs and abdomen can be inflated and deflated individually by the aid of air compression. The basic principle in the MAST application is to create an artificial peripheral resistance and decrease in transmural pressure. Thus, bleeding is arrested, external vascular space is minimized and organ perfusion is sustained. However, the application of MAST has some undesirable effects such as decreased pulmonary vital capacity. Also abdominal disconfort is encountered in some patients. The main disadvantage is the fact that the pressure in MAST is uniformly applied on all the parts of the human organs, which will of course delay the return of the blood into the recirculation stream and possible trapping of the blood distal to the pressure point.
Another disadvantage of the MAST device is encountered and some delay results thereto regarding the further treatment of the injured person, when the MAST device has to be removed. Moreover, consideration should be given to the fact that this device is quite expensive and not for "one-time" use.